Irrigation systems have been used for applying water to the vegetation. One common use of irrigation systems is for watering of the lawn. Such systems include sprinklers distributed over the area, underground water supply pipes to the sprinklers, and valves to open and close the water supply pipes, and central timing controller to operate the valves in accordance to a stored schedule in the controller. The controller controls multiple valves with each valve typically controls multiple sprinkler heads in a zone. Most controllers sends signals to open and close the valves at designated intervals, typically calculated to provide a uniform and maximum amount of water required for each zone. This scheme of supplying water at a fixed amount throughout a large area can be wasteful since the vegetation area is thus watered automatically regardless of the changes in the need of water. Environmental conditions, such as rain, sunlight, wind and cloud, temperature change, humidity, soil moisture, or even a leakage sprinkler pipe or sprinkler head, can also change the amount of water needed at the time. It is thus beneficial to employ an irrigation system that can take the environmental conditions into account to adjust the amount of water accordingly. The system would provide a significant saving in water, energy, and money to the users.
Control systems for automatic irrigation systems used for landscape and agricultural maintenance are known. Most common types of environmental monitoring and control for irrigation systems incorporate a means of controlling the start time and duration of watering cycles via a central timing controller. Often the environmental control is through seasons such as watering more on dry season and less on rainy season. In conventional control system, the primary means for halting an automatic watering cycle when certain environmental event occurs is by an operator manually suspending the cycle at the irrigation controller. In most situations this proves to be an ineffective means of conserving resources due to the inconsistent and inefficient methods followed by the operator. In fact, quite often the operator ignores the need to suspend the watering cycle altogether, and in some cases neglects to resume the watering cycle when required, leading to both over-watered and under-watered landscaping. Operator interruption is also less effective since the controller are normally programmed to operated at the very late evening or early in the morning, where most people would be at rest.
It is because of this unreliable and inconvenient manual method that environmental sensors were developed that allow for an automatic interruption of the controller due to an environmental condition. The use of sensors for irrigation systems has proven to be an effective and economical method of conserving water, energy, and money.
Existing automatic sprinkler controllers for residential and commercial applications are typically wired so that a central controller provides drive signals to each valve in the system to supply water to the sprinkler heads supplied by the valve. Thus, all sprinkler heads connected to a valve emit water at a fixed rate when the valve is turned on. The duration that the valve is turned on determines the amount of water applied to the area covered by each sprinkler head. The irrigation system can be divided into multiple zones for watering. Each zone may contain one valve, or many valves. Each valve is connected to multiple sprinkler heads. When a valve is activated, all the sprinklers connected to the valve will emit water at a fixed rate and in the same time duration.
The amount of water needed for different zone, or areas of the irrigation system is different, based on the location and the geography of the area. The moisture level, the amount of sunlight received at each zone, can be different from each other. The amount of water needed and correspondingly the valve on duration required for the sprinkler heads may be different in the zones. For example, one half of a zone may be in the sunny area while the other is covered by a deep shade. In this case, the sunny section of the zone will require more water than the shaded section of the zone. This is often addressed by using sprinkler heads that have different (but fixed) flow rates. The heads for the sunny section could have 0.2 gallon per minute flow rate and the heads for the shady section could have 0.1 gallon per minute flow rate. Another way is to have different zones with the same flow rate but with different timing. However, this does not accommodate changes over time like changes in shading or plan materials.